Sphingomyelin is a type of phospholipid found abundantly in milk and accounts for approximately 30% of phospholipids in cow milk. Sphingomyelin has a structure in which phosphocholine is bound with a ceramide skeleton composed of sphingosine and fatty acid, and has been known to be also found in the brain or nervous tissues. Moreover, sphingomyelin has been reported to be also contained in small amounts in food such as yolk.
Sphingomyelin has been known to influence cell growth or differentiation in vivo via the signal transduction system. Moreover, it has also been suggested that sphingomyelin has an effect of suppressing reduction in protein kinase C activity attributed to aging and is effective for the prevention or treatment of Alzheimer-type memory disorder (Patent Document 1). However, its effect of improving learning ability in a general sense has not been known by any means. It has further been known that sphingomyelin has an effect of improving lipid digestion/absorption function associated with aging (Patent Document 2). However, its other effects have been little known. Therefore, the development of a pharmaceutical agent, a food and drink product, or feed comprising sphingomyelin as an active ingredient has been expected.    Patent Document 1: Japanese Patent Laid-Open No. 2003-146883    Patent Document 2: Japanese Patent Laid-Open No. 11-269074